Air conditioning systems have been in place for many years. Typically, such systems comprise an outdoor heat exchanger that includes a compressor and evaporator, an expansion device, and an indoor heat exchanger where cooled refrigerant (e.g. liquefied refrigerant) changes phase to a gas, extracting heat from the air within the structure to make such a phase change.
In general, when the temperature within an air conditioned area reaches a predetermined temperature such as a setting on a thermostat, the compressor and air handler energize to cool the air conditioned area, until the temperature within the air conditioned area reaches another predetermined temperature, typically a few degrees below that set by the thermostat. In this way, an amount of hysteresis is provided to reduce start/stop cycles of the compressor and air handler, providing improved efficiency, operating life, and user experience.
Although there are many factors that affect efficiency and cost of operation, a few factors are considered here within. One factor that affects cost is the overall cost of electricity used in operating the compressor and air handler. These devices are motor-driven and typically consume many kilowatt hours per day. In some parts of the world, electricity prices are tiered, in that, during business hours (e.g. when businesses consume the most energy), the electricity rates are higher than during the hours that many businesses are closed and most people are sleeping. This presents an advantage in operating the air conditioning during these off-peak hours, but unfortunately, with conventional air conditioning systems, this would result in the air conditioned areas becoming too cold during the evening and too warm during the day.
Another factor that needs consideration is temperature differential between the area being air conditioned and the outside ambient air. For example, when cooling an air conditioned area, the higher the ambient air temperature, the more the compressor needs to work to compress the refrigerant, and therefore, the more energy consumption. Generally, at night, the ambient air temperature cools, but the same situation occurs as above, in that, it is not practical to reduce the temperature in the air conditioned area below a certain temperature.
Being that the compressor usually consumes a major portion of the overall electricity budget and the compressor will operate more efficiently when outside ambient air is lowest, there are many advantages to operating the compressor during off-peak hours (e.g. at night), but to do so, an efficient way to store the cold heat is needed that does not require the compressor to run during peak (warmer) hours.
Prior systems utilizing thermal storage required the compressor operate to access the cold heat stored in the thermal storage. Further, such systems generally store cold heat (e.g. extract heat) in a fluid by decreasing the temperature of the fluid which has limited efficiency.
What is needed is a system that will efficiently store cold heat and retrieve the cold heat when conditions indicate a need to do such.